The present invention relates to the aircraft flight management system art and, in particular, to an improved flight management system which responds to failure of all flight management computer (FMC's) to link the control display units (CDU's) such that execution of a modified flight plan in one CDU is automatically transferred to the remaining CDU's.
In modern commercial aircraft, a flight crew makes flight plan entries and modifications through a Flight Management System - Control Display Unit (FMS-CDU). The FMS-CDU is an electronic module containing a keyboard on its lower face half and an electronic display on its upper face half. By keying entries into the keyboard, the flight crew can build or modify a route into the flight management computer (FMC) by typing in a series of waypoints, which route is then displayed, in text form, on the upper half of the FMS-CDU display.
An additionally provided display is a navigation (map) display. In contrast to the text display of the FMS-CDU, the navigation display graphically depicts the selected waypoints along the desired route. Thus, as the flight crew types entries into the FMS-CDU, these are then displayed graphically on the navigation display.
Current flight management computers (FMC's) on commercial aircraft provide for the construction of a variety of flight plans, consisting of point-to-point leg segments, direct segments and procedural maneuvers. The FMC provides an output of the flight plan to the navigation display map, where the flight plan is depicted graphically.
Aircraft may be provided with one or more FMC's. In the event that all onboard FMC's become inoperative, there are provisions on many aircraft for the associated Control Display Unit (CDU) to utilize its own internal memory and computing capability to operate in an "alternate navigation" or "CDU navigation" mode. In the alternate navigation mode, the CDU stores in its own internal memory the original, or initial flight plan which resided within the FMC just prior to FMC failure. Now, in the alternate navigation mode, the CDU provides for continued display of the flight plan on its associated navigation display and provides continued capability for the flight crew to make further changes to the flight plan. In this event, each CDU is linked to its respective navigation display map.
A serious limitation with existing aircraft, however, is that in the alternate navigation mode, flight plan changes made on one CDU are not communicated to the other CDU's and, as such, the flight crew must retype all changes into the other CDU's each time a flight plan change is made so that the flight plan in all CDU's, as well as the displayed flight plan on the navigation displays are synchronized.
The burden on the flight crew to repetitively enter the same flight plan into all CDU's is burdensome and subject to the introduction of human error.